The invention generally relates to a catheter system for performing transluminal angioplasty procedures and the like and is more particularly directed to a steerable dilatation catheter having advantages not found in conventional "fixed wire" catheters or "over-the-wire" catheters.
A number of vascular conditions may be treated by percutaneous transluminal coronary angioplasty in which a balloon catheter is routed through the vascular system and positioned across a stenotic lesion. The balloon is then inflated with a fluid to compress the lesion against the artery wall in order to increase its effective luminal diameter.
Apparatus suitable for such procedures currently available can be classified as either a "fixed wire" catheter system or an "over-the-wire" catheter system. A typical "fixed wire" catheter system such as described in U.S. Pat. No. 33,166, dated Feb. 20, 1990, includes a guide wire with a dilatation, or working, catheter permanently fixed thereto. The distinctive advantage of this type of catheter is its relatively low profile, or small overall outer diameter, which enables its use in smaller arteries and in situations with more advanced stenosis in which an artery may be closed to such an extent that a larger diameter catheter, such as an over-the-wire catheter, may not be suitable.
The fixed wire catheter system is not without disadvantage. Because the dilatation catheter is fixed to the guide wire at a distal end thereof which includes a flexible steering portion or tip, the tip itself is necessarily fixed, as well as it's length, thus limiting the steerability of the fixed wire catheter. In addition, since the fixed wire dilatation catheter system must be rotated, both the wire and the balloon are is subject to distortion, particularly "balloon wrapping", due to the rotation thereof which may result in non-uniform inflation, limited ability or even inability for inflation and deflation thereof.
In addition, with a fixed wire system the working catheter cannot be replaced over the guide wire which can be left in situ to establish an established path through the vascular system as hereinafter described.
An over-the-wire catheter system, such as described in U.S. Pat. No. 4,540,404, utilizes a separate guide wire. The guide wire may first be inserted into a vascular system, and thereafter, a dilatation, or working, catheter may be inserted thereover, until a balloon member thereof is positioned across the stenotic lesion. Advantageously, because the guide wire is not fixed to the working catheter, the guide wire and working catheter may be inserted and withdrawn independent of each other. Thus, if necessary, the guide wire can be manipulated independently through a particularly curvaceous artery. In addition, once the guide wire is in place, the working catheter may be replaced as may be required to change it for a working catheter with a different or larger balloon during the angioplasty procedure. In view of these advantages, the over-the-wire system has been considered more "user friendly" than a fixed wire system.
Similarly, because the guide wire may be independently inserted and removed from a vascular system, if a change in a tip shape, size or type is deemed necessary to facilitate advancement or access, the guide wire may be removed, leaving the working catheter in place which subsequently provides an open channel for the replacement guide wire. Once the guide wire is positioned past the stenotic lesion, the working catheter can then be positioned to place the balloon portion across the stenotic lesion for inflation. After deflation and removal of the working catheter, the guide wire may be left in place, enabling reinsertion or exchange of the balloon catheter if necessary for a repeated angioplasty procedure. Alternatively, if the guide wire is removed leaving the working catheter, the lumen thereof, through which the guide wire had passed, is now available for monitoring or other uses.
The present invention is directed to a fixable wire catheter having a number of advantages, not available in prior art devices, as will hereinafter be described in greater detail.